The “cloud computing” has become a popular application in the world. Many applications and services using the cloud computing have been developed to make our life more enjoyable. At the same time, the mobile devices have made themselves a necessary tool of everybody's everyday life. To meet the various needs of the users, mobile devices are designed to provide multiple functions, with their hardware components being more powerful and user-friendly. As people are pursuing for more gorgeous human-machine interfaces and complicated application services, next-generation mobile devices will persist in the significant improvements of computation, display and communication capabilities. However, such a trend makes the mobile devices that provide the interactive applications require significant energy consumption, thereby facing a severe challenge in the usage time.
Among the applications that the mobile devices provide, mobile users have been increasingly addicted to multimedia streaming applications and the ability to disseminate videos via social network communities. A 2010 report forecasts that mobile data traffic will double every year in the following few years and that video streaming will account for almost 66 percent of the data traffic by 2014. Such user behavior would lead to a significant increase in the energy consumption of the mobile devices, especially with the users' strong demands for larger, higher-resolution screens. Recent studies on the mobile user behavior indicate that most electric power used in the mobile devices is consumed by the backlight that illuminates the screen of the mobile devices. In order to save energy, so to extend the usage time of the mobile devices, reducing the power consumption of the backlight shall be first considered.
In saving the energy consumed by the backlight, many solutions have been suggested. As the display subsystem needs to stay in active mode for as long as the video stream is displayed, an ideal method to reduce or to minimize the energy consumption of the displaying system is to dim the backlight illumination without adversely impacting the user's visual experience. A video stream comprises a series of image frames. An intuitive way to determine the needed illumination level is to treat a video stream as a collection of image frames and apply a backlight illumination level (hereinafter, the “backlight level”) to each image frame. However, in most video applications, the dimmest backlight level may vary significantly across consecutive frames. Changing the backlight illumination level arbitrarily over a number of frames may result in the flickering effects and affect user perception. To resolve this problem, some approaches determine the backlight level for an image frame, taking into considerations the preceding frame's pixel values or illumination values and backlight level. The drawback of this strategy is that switching the backlight level frequently may introduce the inter-frame brightness distortions to the video stream.
In the hardware side, the light source requires reaction time in changing the backlight level. Changing the backlight levels at a high frequency is not acceptable. An approach that groups the image frames of a video stream and determines a common backlight level for each group is proposed by Pasricha et al. See Pasricha et al.: Dynamic Backlight Adaptation for Low-Power Handheld Devices, IEEE Design & Test of Computers, 21(5):398-405, 2004. As a result of this solution, the backlight level of a scene may change suddenly, if the frames comprising the scene are partitioned into different groups. To solve this problem, Cheng et al. proposed an approach that quantizes the number of backlight levels to eliminate small backlight fluctuations during a scene. See Cheng et al.: Quality-Based Backlight Optimization for Video Playback on Handheld Devices, Advances in Multimedia, 2007. This and other proposed technologies, however, determine the backlight level of the image frames based on the characters of the frames and their adjacent frames, whereby the energy consumption of the full video stream is not considered and verified. In addition, the determination in the backlight levels requires higher calculation capabilities and operation time. In some cases, to calculate the backlight levels of a video stream of 2 minute long at 550-650 kbps would take about 5 minutes if by a mobile device. Needless to say, the power consumed in the computation would not justify the power saved by adjusting the backlight level.
It is therefore necessary to provide a novel energy saving system and method for mobile devices, to provide effective and efficient tools for the mobile device to save its power consumptions.
It is also necessary to provide a system and method that determines the power consumption policies of the mobile devices, when a video stream is being downloaded or displayed.
It is also necessary to provide a system and method to determine the backlight illumination policies of a video stream, so to minimize the total power consumptions of the mobile devices that display the video stream, while the quality of the video stream as displayed is maintained.
It is also necessary to provide a system and method for saving the energy consumption of the mobile devices, while maintaining the operational quality of the mobile devices.